碩士 / 國立臺灣大學 / 地質科學研究所 / 91 / The intramountain basins of Puli and Yuchi, central Taiwan are developed during middle Pleistocene. Basin deposits of Puli are mainly massive alluvial gravel beds of about 400 m. The gravel beds are intercalated by two fine-grained layers, one is more than 8 m thick, the other, 4 m thick, as found cropping out below the Dapingding terrace. Morphologically, three steps of terraces exist in the northwestern part of Puli Basin, the highest, the middle and the lower. Imbrications of gravel of the upper two steps show that they derived from north or northwest while that of the lower terrace show the deposits come from the westward draining Mei-Hsi. In the Yuchi Basin, only one ancient surface exists above the flood plain. The ancient surface has been dissected. Based on the study of sediments exposed by dissection, sedimentary facies changes from fan to shallow gravel-bed braided river and finally to lacustrine-swamp northward. The basin deposits are mainly carried by three rivers from the south. Radiocarbon dates indicate that the basin surface was dissected after 6 ka.
Warping of the terraces helps us to recognize one anticline, two thrusts in the Puli Basin and one anticline in the Yuchi Basin. The nearly N-S trending thrusts and anticlines tilt the terrace surface and develop linear scarps. Evidences from geomorphology, pollen stratigraphy and radiocarbon dates delineate a N-S trending fault in the central part of Puli and Yuchi Basins. The fault is probably sinistral, with the component of down-slip in the eastern block.
Kriging method and DEM data of the remnant surface of fluvial-lacustrine deposits are served to estimate the height of original surface of Yuchi Basin. Comparing the recovered ancient surface and the recent topography, the total denudation volume of the fluvial-lacustrine deposits is about 5.47x108 m3 since 6000 years ago. The river cutting rate is about 0.8-2 cm /year.
| Identifer | oai:union.ndltd.org:TW/091NTU00138013 |
| Date | January 2003 |
| Creators | Bing-Cheng Chen, 陳炳誠 |
| Contributors | Ping-Mei Liew, 劉平妹 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 97 |
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